Soil organic carbon (SOC) plays a vital role in soil fertility and is important for its contributions to mitigation and adaptation to climate change. The present study was undertaken to estimate the SOC stock in soils under different land uses of Cauvery Delta zone of Tamil Nadu. Four different land uses were selected for the study viz, Forests, Agriculture, Agro-forestry and Plantations. Soil samples were collected from Madukkur and Kalathur soil series of Cauvery Delta zone for soil carbon analysis. The soil samples were fractionated into three aggregate size classes viz., macro-aggregates (250-2000µm), micro-aggregates (53-250 µm) and silt and clay sized fraction (<53 µm). At 0-30 cm depth, the forest land use stored the maximum SOC stock in the different size fractions viz. macro-sized fraction (73.0 Mg ha-1), a micro-sized fraction (76.0 Mg ha-1) and silt+clay sized fraction (77.0 Mg ha-1) in Madukkur series. Agriculture land use registered the lowest SOC stock. Among the different size fractions, silt+clay sized fraction (< 53 µm) retained the maximum SOC in all the land uses. In Kalathur series also, maximum soil organic carbon stock was recorded in forest land use. The data generated in the study will be beneficial to the user groups viz., farmers in identifying the most suitable land use for enhancing the storage of soil organic carbon thereby improving yields of crops and trees.

To assess the impact of nutrient ratios N/P, N/K and N/S on sugarcane productivity, a survey was conducted during its grand growth stage (October, November and December) influenced by various yield levels based on soil quality zones in Theni district of Tamil Nadu, India. The leaf samples were collected from cane yielding zones of the district was classified into three categories viz., low yielding (less than 75 t ha-1), medium (75 to 100 t ha-1) and high yielding (more than 100 t ha-1). Computation of nutrient ratios for sugarcane at its grand growth stage implied that the mean N/P, N/K and N/S ratios 8.31, 1.60 and 15.0 respectively in the third leaf of sugarcane in the high yielding zone resulted in maximum cane yields compared to relatively higher ratios in the top dewlap leaves from soils of low soil quality category which indicates that maintenance of high quality in sugarcane soils influences crop nutrient uptake, optimum nutrient ratios, the yield and quality of sugarcane.

No abstract